Damper bar for filamentary cathodes



1 Oct. 9, 1951 SIMPSON 2,570,606

DAMPER BAR FOR FILAMENTARY CATHODES Filed May 12, 1949 INVENTOR ATTO EYPatented Oct. 9, 1951 DAMPER FOR FI LAMENTARY CATHODES Kenneth H.SimpsonpMaplewood, N. J., assignor to Radio Corporation of America, acorporation of Delaware Application May "12, 1949, Serial No. 92,788

1 My invention relates to electron dischargedevices having filamentarycathodes and more particularly to a damping means for such cathodes toprevent vibration thereof.

Some electron discharge devices. employ two spaced parallel insulatingplates, usually of mica, for suitably spacing a concentric array ofelectrodes. Where a filamentary cathode is ineluded in the device it isusually threaded through apertures in the plates and engaged at one orboth ends thereof by suitable tensioning means for maintaining thecathode or filament taut between the plates. To prevent vi- 5 Claims.(01. 313269) bration of the taut filament various expedients have beenproposed including mica strips and insulated metallic damper bars forengaging a portion of the filament intermediate the plates.

Such expedients, however, have not proven completely satisfactory. Forexample, some electrode mounting procedures require that the electrodesother than the cathode .be first assembled in a mount together with thecathode damping means. In such instances the subsequent mounting of thecathode in the mount becomes difiicult due to the necessity of observingcare that the cathode filament is threaded properly with respect to thedamping means. Usually the damping means is designed to engage thecathode by a critical side or portion thereof and to assure suchengagement recourse sometimes has been made to special vibrating jigsfor guiding the filament in a predetermined path between the insulatingplates referred to for proper orientation of the filament with respectto the damping means. The necessity for the high degree of care andspecial jigs'that has characterized prior practices in mountingfilamentary cathodes in assemblies that include damping means, adds tothe cost of manufacture by slowing down the cathode mounting operationand increasing the expense of equipment.

While this difliculty has heretofore been recognized and attempts toovercome it have been made, such attempts have not provenfullyacceptable. Thus, one proposal involves the use of a wire hook havinginsulation thereon for engaging the filament by either one of oppositesides of a hook. This arrangement permits greater freedom in threadingthe filament in the mount since care need not be exercised to positionthe filament to a particular side of the damper hook. However, anobjectionable feature of this proposal resides in th'ejneed for arelatively large structure for the damper hook,

since it includes angularly disposed portions re quiring a wider areafor accommodation than is sometimes provided by the electrode adjacentthe cathode. For example, when a wound control grid is employed thedistance between opposite portions of the turns thereof maybe less thanthe lateral extent of the damper hook between these portions. Since thegreater portion of the damper hook is usually provided with a relativelythick coating of insulation to insulate it from the cathode thisproposal restricts the spacing between adjacent turns of the grid to amagnitude greater than the thickness of the coated hook. This type ofdamping means cannot therefore be used in instances where the controlgrid is closely wound or where it is of relatively small overall sizesuch as in miniature electron discharge devices.

Another objection to this and' other types of damping means of the priorart is that the form of the damping means must be very carefully madeand the mounting of the damping means must be accomplished in a verycritical manner to assure proper engagement therewith by the filament.

Accordingly, it is the object of the present invention to provide animproved damping means for filamentary cathodes.

A further object is to provide an improved damper bar for properlyengaging a filamentary cathode in any one of several positions in whichthe cathode may be threaded in a mount. f

Another object is to provide a straight damper bar for a filamentarycathode that is suitable for relatively cramped space conditions in 'amount.

A further object is to provide a straight damper bar that is properlymounted in an electrode assembly with a relatively small degree of care.

Another object is to reduce the cost of manufacture of electrondischarge devices having filamentary cathodes by providing an'improvedstraight damper bar that is easily and quickly mounted in the assemblyof the device and that permits a rapid and accurate mounting of-thecathode in the device.

Further objects and advantages of the invention will become apparent asthe present description proceeds.

Referring to the drawing for a better under standing of the invention;

Figure 1 is an elevation partly in section of an electron dischargedevice employing the im proved damper bar of the invention;

Figure 2 is a transverse section along 2-2 of Figure 1;

Figure 3 is a longitudinal section along 3-3 of Figure 2; and

Figure 4 is a modification of the manner in which my novel damper barmay be mounted.

Referring now in more detail to the drawing, there is shown in Figure 1thereof a miniature type of electron discharge device including anenvelope l closed at one end by a fiat stem H and having an electrodemount comprising anode I2, grid 53 supported on grid side rods I4, I5and a filamentary cathode [6. The electrodes referred to are mountedbetween insulating spacer plates H, l8 and are connected to suitablelead-ins 19. The filamentary cathode IB is tcnsioned by a spring member20, sup: ported on rod 2!, which is fixed to spacer I! by eyelet 22. Thespacers ll, 18 are provided with suitable apertures for receiving theside rods i4, i5 and for threading the filament l6 therethrough. Theside rod and filament apertures referred to are preferably disposed in aplane normal to said spacers for appropriate disposition of thefilamentary cathode with respect to the grid.

According to the invention, means are provided for damping vibrationsthat otherwise might occur in the portion of the filamentary cathode itthat extends between the spacers ll, i8. In one embodiment of theinvention as shown in Figures 1, 2 and 3 the damping means comprises astraight damper bar 23 having a coating of insulation 24 intermediatetwo bare end portions thereof.

The damper bar is preferably disposed between grid side rods l4, 15 insuch a manner that one bare end portion engages one side of side rod l4and the other bare end portion of the damper bar engages the oppositeside of rod 15. The damper bar 23 may be fixed to one or both of siderods l4, [5 as by welding shown at 25 and 26 in Figure 2.

This manner of mounting of the damper bar according to the inventioncauses the intermediate insulated portion thereof to symmetrically crossthe axis of suspension of the filamentary cathode [6 as shown in Figure3. Thus, at the point where the damper bar crosses said axis anequilateral extent of said bar occurs on opposite sides of the axisreferred to. This has two advantages. It permits the mounting of thedamper bar on the side rods with a minimum of care. Thus, properpositioning of the damper bar is assured by merely causing its bare endportions to engage opposite sides of the grid side rods l4, l5 andfixing one or both end portions to the side rods. This reduces thedemand for skill on the part of the operator and speeds up the mountingoperation, resulting in substantial economies in manufacture.

A-nother advantage of this arrangement is that the filamentary cathodeI6 is properly engaged by either of two opposite sides of the damperbar. There is therefore no need to employ expensive jigs and resort tothe tedious and comparatively slow operation of threading the cathode soas to lie to one particular side .of the damper bar. This reduces theoperation of mounting the cathode to such simple terms that all theoperator needs to positively provide for is the threading of the cathodethrough the two registering apertures provided for in the spacers -11,l8. This contributes to a further reduction in the cost of making anelectron discharge device wherein a filamentary cathode is desirably.damped.

It will be noted that the straight damper bar' 23 with its insulation 24requires a space between the side rods l4, 15 that is characterized by arelatively small lateral extent. This feature renders the damper bar ofthe invention particu larly suited for devices of the miniature typewhere the space defined by control grid [3 is relatively small. Inaddition, the damper bar 23 is comprised of a wire or rod having arelatively small cross section at its end portions so that it issuitable for use with relatively closely wound grids without interferingwith any grid turns.

A modification of the invention is shown in Figure 4 which involves adiiferent mounting of the damper bar 23 on the grid side rods [4, I5than that shown in the figures heretofore discussed. In this instancethe damper bar 23 is mounted to engage analogous sides of the side rodsi4, i5. This disposes the greater portion of the insulated intermediateportion 24 of the damper bar to one side of the axis of suspension ofthe filamentary cathode 16. In some types of miniature electrondischarge devices this manner of mounting of the damper bar results in arelatively close spacing between one side of the damper bar and one sideof grid [3. This spacing may be so close as to prevent threading of thefilamentary cathode l6 therethrough. This has the advantageousconsequence of permitting the cathode to be threaded only in a path thatis adjacent the opposite side of the damper bar which side is spacedfarther from grid [3 than the first mentioned side. the structure ofthis modification inherently limits the position of the cathode to oneparticular side of the damper bar contributes to ease, rapidity andaccuracy of the cathode mounting operation which add to economicalmanufacture of an electron discharge device in which it is used.

It will be noted that the magnitude of deflection of the filamentarycathode 16 from its axis of suspension in the two embodiments describedis different. Thus, when the damper bar engages one of opposite sides ofthe grid side rods as shown in Figure 2, a greater lateral deflection ofthe cathode occurs than where the damper bar is connected tocorresponding sides of the side rods as shown in Figure 4. In somelarger types of tubes opposite portions of the grid are spaced by arelatively large magnitude that would not permit the relatively closespacing between the insulated portion of the damper bar and the grid asshown in Figure 4. In such case the cathode would find a path on eitherside of the damper bar. However, the engagement of the cathode by oneside of the damper bar would result in a greater magnitude of deflectionthan would occur if the opposite side of the damper bar engages thefilament. This latter condition is undesirable since it might causedifferences in the characteristics between several tubes of the sametype. Consequently, in such instances, the diagonal mounting of thedamper bar on the side rods as shown in Fig. 2 would be necessary. Thegreater deflection that this would impart to the cathode is notobjectionable in tubes of relatively large size since the deflectionwould be I small in relation to the size of the tube.

However, in some small size tubes the deflection afiorded by thearrangement of Fig. 2 might be excessive. In such cases the arrangementshown The fact that l in Fig. 2 which provides for a smaller deflectionof the cathode is preferred. As indicated before herein, the mounting ofthe damper bar as shown in Fig. 4 in addition to reducing the degree ofdeflection of the cathode as required in a small tube, also utilizes toadvantage the small size of the tube including the relatively closespacing of opposite sides of the grid I3 for restricting the threadingof the cathode to a path that is adjacent one particular side of thedamper bar.

The damper bar of the invention and its manner of mounting are thereforeadvantageous in large and small size electron discharge devices, andlend themselves to particular utility in each of these types of devices.The damper bar is quickly, easily and accurately mounted in a device andpermits in turn quick, easy and accurate mounting of the cathode in thedevice, resulting in appreciable economies in manufacture.

Various additional embodiments of my invention may present themselves topersons skilled in the art without departing from the spirit of theinvention and I desire to include such embodiments within the scope ofthe appended claims.

I claim:

1. An electron discharge device having a filamentary cathode, a gridhaving transverse wires and side rods supporting said wires, two spacerplates having apertures for receiving said side rods and said cathode,said apertures in said two plates being disposed in a common plane, anda straight damper bar engaging said side rods between two of saidtransverse wires and intermediate said spacer plates, said damper barhaving an intermediate portion coated with insulating material and bareend portions, said intermediate portion extending across the axis of theapertures for said cathode for engaging said cathode and deflecting thesame in a plane normal to said common plane for improved operation ofsaid device, one of said bare end portions being fixed to one of saidside rods.

2. An electron discharge device having a filamentary cathode, a gridcomprising a plurality of turns of wire forming a tubular structure,grid side rods lying in a common plane including the axis of saidstructure and engaging opposite sides of said tubular structure forsupporting said turns of wire, whereby the maximum effective portion ofsaid grid is disposed in a plane normal to said common plane, and adamper bar consisting of a straight wire having bare end portionsengaging said side rods and having a coated portion for deflecting saidcathode and restraining vibrations therein in said normal plane, wherebysaid cathode is fixed against relative movement with respect to saidmaximum effective portion of said grid.

3. An electron discharge device having a fllamentary cathode extendingalong the axis of said electron discharge device, a grid surroundingsaid cathode and having oppositely disposed side rods extending parallelto the axis of said electron discharge device, a plurality of turns ofconductors supported on said side rods, a damper bar consisting of astraight conductor having bare end portions engaging said side rods andhaving a coated portion intermediate said ends, said coated portionengaging and deflecting said filamentary cathode intermediate its endsand away from the axis of said device and restraining vibrations thereinin a direction normal to said axis whereby said filamentary cathode isfixed against relative movement normal with respect to the surface inwhich the conductors of said grid lie. E has 4. An electron dischargedevice having a filamentary cathode, a tubular electrode surroundingsaid filamentary cathode and having opposite portions of maximum effecton electrons emitted by said cathode, and a damper bar consisting of astraight wire having bare end portions engaging opposite portions ofsaid tubular electrode intermediate said first named opposite portions,said damper bar having an insulating coating thereon intermediate itsends for engaging and deflecting said cathode, whereby said cathode isfixed against vibratory movements with respect to said first namedopposite portions for improved operation of said device.

5. A sub-assembly for an electron discharge device comprising a controlgrid including a plurality of spaced turns of wire forming a tubularstructure and grid side rods at opposite sides of said structure forsupporting said turns of wire, and a straight damper bar consisting of astraight wire having bare ends engaging leading sides of said side rodsduring rotation of said grid in a predetermined direction andintermediate two F adjacent turns of said wire, whereby said damper baris adapted to be mounted on said grid by automatic mechanized means andextends across the axis of said tubular structure, an intermediateportion of said damper bar having an insulating coating adapted toengage and deflect a filamentary cathode supported axially of saidtubular structure, in the plane of maximum control by said grid forimproved operation of said device.

KENNETH H. SIMPSON.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 1,572,726 Kelly Feb. 9, 19261,636,239 Metcalf July 19, 1926 1,886,991 Van Horne Nov. 8, 19321,930,563 Ponte Oct. 17, 1933 2,259,703 Miller Oct. 21, 1941 2,266,080Rockwood Dec. 16, 1941 2,303,277 Ishler Nov. 24, 1942 2,303,278 IshlerNov. 24, 1 942 2,350,003 West May 30, 1944 2,358,829 Rockwood Sept. 26,1944 FOREIGN PATENTS Number Country Date 389,176 Great Britain Mar. 16,1933 515,288 Great Britain Nov. 30, 1939

